I am interested to know as well. I have found a Desert Chupaxabra gem yesterday that can level a one star gem to five. I did not actually level a gem though since I relly dont know what gem a Cleric loke my build should be using with max level right now. Should I use those kinds of gems to level other gems or should it be kept for selling?

Every monster gem you put as mats = 15, 500 exp
Every material item you put as mats = 5 exp
As for equipments = it depends on the item/level
This is my methods.
1. Find a farming spot that has many mobs and respawn quick.
Example = Miner's Village
there's a boss and many puny mobs that drop material items and equipments that can be use as mats to level up gem.

2. If you have a lot of money I mean a LOT of money you can buy material items in market that is a really low price to use as mats to level up the gem

does every monster gem equal to 15k exp or does it depend on what monster gem it is? I've only acquired two monster gems, the first one I lost when I died and the other one is that Desert Chupacabra Gem that I mentioned earlier. I have not tried using the first on I got to level my gem, it was a Keppa gem I think, if I did not get the name wrong.

This is probably the most dumbest question of all so please do not kill me *bowing with utmost embarrasement* how does gem leveling work? Do i need to equip it to a weapon before it levels or do i enhance it first while in rest?

You level the gem while your resting (hotkey 3). In this menu, you place the gem that you want to level and then the materials that you want to use to level it. You can use cards, materials, equipment or other gems-- each of which give varying amount of xp to the gem. As you level it, the gem increases in the stats it provides to you.

Once you've leveled it sufficiently, you can equip it to a weapon that is slotted.

You level the gem while your resting (hotkey 3). In this menu, you place the gem that you want to level and then the materials that you want to use to level it. You can use cards, materials, equipment or other gems-- each of which give varying amount of xp to the gem. As you level it, the gem increases in the stats it provides to you.

Once you've leveled it sufficiently, you can equip it to a weapon that is slotted.